Watch case



March 29, 1966 M. LEDERREY 3,242,664

WATCH CASE Filed NOV. 8, 1961 2 Sheets-Sheet 1 I/VVEN'roR March 29, 1966LEDERREY 3,242,664

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United States Patent 3,242,664 WATCH CASE Marc Lederrey, Granges,Soleure, Switzerland, assignor to Schlup & Cie S.A., Berne, Switzerland,a joint-stock company Filed Nov. 8, 1961, Ser. No. 150,962 12 Claims.(Cl. 58-88) This invention relates to watch cases and in particular towrist-watch cases having an attractive appearance.

The finest watch cases known in the art are made of gold and they aresometimes even furnished with enamel. These known watch cases arehowever very expensive and they have, moreover, to be carried withutmost care. Therefore, they would immediately be damaged, if they werecarried in everyday life for manual labor or sport.

The only way hitherto known in the art for obtaining a watch caseresistant to strong conditions of wear was to make it of steel and inparticular of stainless steel. However, if such a watch case isrepeatedly submitted to frictional engagement with hard objects, itsfinely polished outer surface portions exposed to contacts with foreignobjects will soon be scratched and the watch case will neverthelesssuffer substantial damage.

It is therefore an object of the invention to provide a watch case withan outer area reinforced in such a manner that it will not be damaged byimpacts or frictional engagements with hard foreign objects.

It is also an object of the invention to provide a watch case with areinforced outer area resistant to the oxidizing agents of theatmosphere.

Another object of the invention is to provide a watch case with aprotecting outer area having a very attractive and durable appearance.

Still another object of the invention is to provide a watch case with anouter protecting and ornamental area (zone, portion or piece) consistingof a material containing a metal carbide being harder than topaz, suchas tungsten or titanium carbide.

Metal carbides such as tungsten or titanium carbides are well known fortheir particularly high hardness and they have accordingly been usedhitherto for tools on an important scale. Till now, nobody has, however,imagined that workpieces of common use could be manufactured on acommercial scale with such a material. This is probably due to the factthat a material containing a tungsten or titanium carbide cannot beeffectively machined after it has been sintered by normal means. Diamondis indeed the only material by means of which particles can be removedfrom a workpiece made of a sintered tungsten or titanium carbide powderand even with a grinding wheel loaded with diamond powder, the amount ofmaterial which can be removed from such a workpiece during a reasonablylong period is extremely Furthermore such a machining operation wouldinvolve too strong a wear of the grinding wheel. By means of electricsparks produced in a cell like those used for electrolytic polishing anoticeable amount of material can be removed from a workpiece consistingof a sintered tungsten or titanium carbide, but this method is very slowand can therefore only be resorted to with the manufacture of tools, thehigh cost of which will be compensated by the great number of workpiecesit will be possible to manufacture by means of these tools.

To form a piece of a material containing tungsten or titanium carbide,an intimate mixture is first prepared, for instance in a ball mill, witha powder of the metal carbide and a powder of a bonding metal such asfor instance cobalt, the particles of both powders there-by having verysmall sizes. This mixture is then submitted to a preliminary sinteringso as to form a solid block which can however still be machined easilyfor instance by means of a diamond tool. Pieces having a shape similarto that of the workpieces which are to be manufactured are then cut fromsaid block and introduced into a furnace to carry out the finalsintering thereof. During the last operation a shrinkage of about 20% byvolume can be observed. After this operation the pieces obtained receivetheir final hardness. Because of the important shrinkage observed, itdid not appear very easy to form workpieces of hard metal with exactsizes by the method described. For the same reason it was alsoconsidered that workpieces of tungsten or titanium carbide formed bysintering should have the same overall cross-section to prevent theshrinkage from being accompanied by a distortion. The above mentionedreasons are probably those which till now kept manufacturers from makingtungsten or titanium carbide workpieces of common use on a commercialscale and in particular from making watch cases of a sintered hardmetal. Watch cases must of course have exact inner sizes and theircross-section varies between wide limits because of the wrist-bandattaching lugs which have to be made integral with the case.

In spite of all the existing very strong prejudices against the idea ofmanufacturing watch cases of hard metal carbides, it has now beenobserved that these pieces, through their substantially varyingcrossasection, can be made on a commercial scale without greatdifficulties and with a quite satisfactory precision. To avoiddistortions in sintering, the pieces are laid on a crucible, forinstance of graphite, and a small weight is set thereupon.

The invention will now be described in detail with reference to theaccompanying drawings which constitute a diagrammataic'al showing ofthree embodiments of the invention, which are however only disclosed byway of example.

In the drawings:

FIG. 1 is a perspective view of the first embodiment,

FIG. 2 is a part sectional view on a larger scale of the watch caserepresented in FIG. 1,

FIG. 3 is a bottom view of a piece of said watch case,

FIG. 4 is a side view partly in section of the watch case piecerepresented in FIG. 3,

FIG. 5 is a perspective view analogous to that of FIG. 1 showing thesecond embodiment,

FIG. 6 is a part sectional view on a larger scale of this secondembodiment, and

FIG. 7 is a perspective view of the third embodiment.

The watch case of the first embodiment comprises an outer piece 1 ofhard metal consisting of sintered tungsten carbide powder. This piece 1is represented separately in FIGS. 3 and 4. As shown in FIGS. 1 and 2this outer piece 1 constitutes the upper portion of the watch case, i.e.the portion which is particularly exposed to wear by coming in contactwith foreign bodies. The watch case outer piece 1 is provided with apolished upper inner flat annular surface portion 2 surrounding thewatch glass 3. Piece 1 also comprises a polished upper outer conicalsurface portion 4 adjacent surface portion 2 and extending downwardtherefrom. The two surface portions 2 and 4 constitute the uppermetallic surface of the watch case and therefore the most important partof the visible outer portion thereof. Piece 1 further comprises an outerside surface extending downward from the periphery of surface portion 4,in a direction substantially parallel to the watch case axis. It can benoticed in FIG. 1 that this side surface comprises two portions eachextending on one of the longer sides of the watch case and havingsubstantially the same overall width. FIG. 1 also shows that said sideportions not only extend over the watch case part adapted to receive thewatch movement but also along projections 5 which serve as wrist-bandattaching lugs. As viewed in FIG. 3 piece 1 comprises two pairs of lugs5 extending in diametrically opposed directions from the annular centralportion of said piece. A half cylindrical recess 6 is formed in one ofthe longer side portions of piece 1 to serve as a lodging for theWinding and hand setting member 7. The inner surface of piece 1comp-rises three cylindrical bearing surfaces 8 which are separated fromone another by two fiat shoulders 9. Piece 1 finally comprises two websections 10 each extending over the two lugs of one of said pairs andconnecting these two lugs to one another. As shown in FIG. 1 the uppersurfaces of web sections 10 form part of the conical upper surfaceportion of piece 1. As more precisely explained hereinafter these websections 10 are intended for preventing a distortion of piece 1 duringsintering.

To manufacture the Watch case upper piece 1, a preliminary sinteredblock of tungsten carbide is first prepared as explained above. A piecehaving a shape similar to that of FIG. 1 is then cut out of that blockby the usual techniques. This cutting ope-ration can be carried out bymeans of a diamond tool without excessive wear of said tool, because thepreliminary sintered block has not yet received its final hardness. Theshape of the piece cut out of said block has to be calculated withrespect to that of piece 1 while considering the shrinkage of about byvolume, which the preliminary sintered piece will be subjected to duringthe final sintering operation. To avoid a distortion of this pieceduring the final sintering operation, it is recommended to lay saidpiece on a crucible having a conical surface and preferably made ofgraphite, the conical surface of the crucible thereby having the sameopening angle as the conical surface portion 4 of piece 1. Moreover, thework piece will have to be pressed on said crucible by means of a weightset on the thick portions of piece 1 represented in FIG. 3. After thesintering operation the piece obtained will only have to be submitted toa usual polishing operation of its upper surface comprising portions 2and 4. This polishing operation can be carried out without anydifliculty because of the simple geometrical form of portions 2 and 4.

To enable attaching a wrist-band to the watch case according to theinvention, blind holes 23 are provided by means of a usual machine wellknown to those skilled in the art in the inner face of lugs 5, beforepiece 1 has been finally sintered. Conventional bars 11 can then bemounted on piece 1 in the same manner as with the known watch cases.

To manufacture a watertight watch case comprising a screwed bottomsection, it is not advisable to make the whole case-band of hardsintered metal, since it would not be practical to provide screwthreadsin such a piece. The watch case represented in FIGS. 1 and 2 thereforecomprises an inner metal ring preferably made of stainless steel 12. Aflange 13 adapted to receive the glass 3, a shoulder 14 serving as anabutting stop for the dial 15, a second shoulder 16 similarly serving asabutting stop for the base-plate of the watch movement 17, grooves 18adapted for receiving latches (not shown) provided for fixing the watchmovement 17 within ring 12, a recess 19 adapted for receiving an outercylindrical portion of the watch case bottom 20, and an abutment 21adapted for receiving a gasket 22 provided for ensuring a watertightseal between ring 12 and bottom 20, are provided in the inner surface ofring 12. Cylindrical bearing surface portions corresponding to thesurface portions 8 of piece 1 and flat shoulders corresponding toshoulders 9 of piece 1 are machined on the outer surface of ring 12.

The outer protecting and ornamental piece 1 and the metal ring 12,adapted for receiving and supporting the glass 3, the watch movement 17and the bottom 20, are rigidly fixed to one another, piece 1 therebyextending above and around ring 12. To perform fixing piece 1 and 12 toone another, the latter could be set with force fit into the former. Tocompensate the unavoidable manufacturing imprecisions, in particular topiece 1, it is however more advisable to glue said two pieces into oneanother, for instance by means of the glue on sale under the trademarkAraldite. The glue layer extending between the corresponding cylindricalbearing surface portions and the corresponding shoulders of both pieces1 and 12 will thereby not only ensure the fixing of said pieces to oneanother but also automatically compensate for the manufacturingimprecisions thereof.

FIG. 2 shows that the glass 3 is formed with a lower bulged surface andwith an upper flat surface. To obtain a watertight seal between glass 3and ring 12, a downwardly extending rim portion of glass 3 is pressed ina radial direction against a cylindrical surface portion of ring 12 bymeans of a strengthening ring, as usual. The depth of flange 13 isthereby chosen in such a manner that the flat upper glass surface willbe located somewhat below the inner upper fiat surface portion 2 ofpiece 1, when the glass 3 and the piece 1 will have been set in place onto ring 12. Piece 1 will thus not only protect the watch case metalsections, but also the glass of this watch case.

In addition to the fact that the inner metal ring 12 can be manufacturedvery easily, for instance on an automatic lathe, this ring has also theadvantage to provide a resilient cushion for piece 1, thereby avoiding abreak of said piece upon a strong impact.

The watch case according to the second embodiment (FIGS. 5 and 6)differs from that of the first embodiment by the fact that the outerarea of the watch case is here protected by means of hard metal elementshaving another shape than in the first embodiment. The watch caserepresented in FIGS. 5 and 6 comprises an annular piece 24 preferablymade of stainless steel and having only its upper surface portionscovered and protected by thin plates 25 and 26 of a sintered tungstencarbide. The annular piece 24 is provided with two pairs of lugs 27, 28projecting in two diametrically opposed directions from said annularpiece and integrally made therewith. As in the first embodiment lugs 27,28 permit attaching a wrist-band 29 to the watch. To permit fixing thehard metal plates to piece 24 and lugs 27, 28, the upper surface of theannular piece 24- is fiat and the upper surface of each lug comprises afirst fiat portion located in the same plane as said flat upper surfaceof piece 24, and a second portion inclined downward with respect to saidfirst portion. Moreover, the second portions of the two lugs of the samepair are located in the same plane. Plate 25 comprises an annularportion 25a and two diametrically opposed ears 25b projecting from saidannular portion. This piece 25 has the same overall thickness, so thatmanufacturing plate 25 does not present any difiiculty. The sizes ofpiece 25 are calculated so that said piece will entirely cover the uppersurface of the annular portion of piece 24 as well as said first flatupper surface portions of lugs 27 and 28. Two plates 26 are furtherfixed over the inclined upper surface portions of lugs 27, 28,respectively. Plates 26 can furthermore be so arranged that they can beset at the side of plate 25, while avoiding any apparent jointtherebetween. Plates 25 and 26 are preferably fixed to their supports24, 27, 28 by soldering. Since plates 26 also have the same overallthickness, they can be manufactured by sintering without any difficulty.

As in the first embodiment, the stainless steel support 24, 27, 23 ofthe hard metal plates 25, 26 constitutes a resilient cushion preventingsaid plates from breaking upon impact. Since plates 25 and 26 have thesame overall thickness, their upper visible surfaces can be polishedtogether, before soldering these plates on piece 24. After the solderingoperation, which can be carried out under a controlled atmosphere bypassing the pieces through a furnace, on a continuously driven endlessband, the watch case described only requires a short finishing operationto burnish their polished surfaces.

Instead of providing the watch case only with an outer reinforced areaconsisting of a hard metal carbide, it could obviously also be madeentirely of said metal carbide as shown in FIG. 7. In this thirdembodiment the watch case comprises a massive piece 30 of sintered metalcarbide having a substantially rectangular shape. Piece 30 is providedwith a central circular lodging adapted for accommodating a watchmovement therewithin. Two recesses 31 are also provided in the twoshorter sides of piece 30 to enable attaching a wrist-band 32 to thatpiece. A bore (not shown) is finally provided across a longer sideportion of piece 30, to ensure the passage of the winding and handsetting stem carrying member 33. The upper visible surface of piece 30is fiat. This surface portion has sizes which are substantially greaterthan those of the glass 34 secured to piece 30. The upper surface ofpiece 30 can be polished in the usual manner, by means of a grindingwheel loaded with a finely divided diamond powder. Markings 35,extending in a radial direction with respect to the central circularopening of piece 30 and corresponding to the horal divisions of thedial, are provided in the upper surface of piece 30. These markings canbe engraved with a pointed diamond tool before the final sinteringoperation. The two longer side surface portions of piece 30 are alsofiat, so that they can easily be polished after the final sinteringoperation.

The cost price of the watch cases according to the invention isobviously higher than that of the stainless steel watch cases known inthe art. This price is however substantially lower than that of goldwatch cases.

The hardness of the material obtained by sintering a tungsten carbidepowder is about 9 in the Mohs scale. Said material is thus harder thantopaz, which is about 8 in the Mohs scale. Sintered tungsten carbide caneven be as hard as Carborundum, which has a hardness of about 9.5 insaid scale. A piece made of sintered tungsten carbide will therefore notbe scratched by the usual materials. Only diamond and, in someinstances, Carborundum are able to scratch such a piece. Moreover,tungsten carbide has the advantage to resist the oxidizing action of thecorrosive agents of the atmosphere.

The improved watch case according to the invention has thus theadvantage to keep its original appearance during a period which ispractical-1y non-limited, even if it is carried under the most extensiveconditions. Its polished outer surfaces will always show the samebrightness and it will never be damaged by scratches.

The watch cases according to the invention can also be given new shapescomprising large polished visible surface portions.

The color of the material consisting of sintered tungsten carbide isdarker than that of steel, thus giving the watch case according to theinvention an original ornamental appearance.

Instead of using tungsten carbide to form the outer area of the watchcase according to the invention, other metal carbides being about ashard as tungsten carbide, such as for instance titanium carbide, couldobviously also be used.

Although some embodiments of the invention have been described in detailwith reference to the accompanying drawings, various changes in theshape, sizes and arrangement of parts will appear obvious to thoseskilled in the art within the scope of the appended claims.

I claim:

1. A watch case having an exposed outer area containing a metal carbideand being harder than topaz.

2. A watch case as defined in claim 1, wherein said metal carbide isselected from the group consisting of sintered tungsten carbide powderand sintered titanium carbide powder.

3. A watch case having an exposed asymmetrical outer '6 surface portion,said surface portion being formed of a metal carbide harder than topaz.

4. A watch case as defined in claim 3, including a metal ring, a watchmovement received therein and a transparent piece supported over saidmovement, wherein said surface portion surrounds said transparent pieceand comprises a metal carbide cover member fixed above said ring andhaving wrist band attaching lugs integrally formed therewith.

5. A watch case as defined in claim 4, wherein said metal carbide covermember has a conical upper face.

6. A Watch case as defined in claim 5, wherein said metal carbide isselected from the group consisting of sintered titanium carbide powderand sintered tungsten carbide powder.

7. A watch case as defined in claim 3, wherein said watch case includesa transparent piece having a flat upper surface, and wherein saidexposed asymmetrical outer surface portion comprises an outer metalcarbide member having an upper portion adjacent said transparent pieceflat upper surface and extending thereabove.

8. A watch case comprising a steel housing member adapted to receive awatch movement therein, said housing member having an upper surfaceportion, said housing member having an exposed metal carbide coveringover said upper surface portion, said metal carbide covering beingsecured to said upper surface portion.

9. A watch case as defined in claim 8, wherein said metal carbidecovering is secured to said upper surface portion by an adhesive.

10. A watch case as defined in claim 8, including a watch movementreceived in said housing member, and wherein said metal carbide coveringcomprises a polished upper inner fiat annular surface portionsurrounding at least a portion of said movement, a polished upper outerconical surface portion extending downward from said flat annularsurface portion, an outer side surface portion extending downward fromthe periphery of said conical surface portion, two pairs of wrist-bandattaching lugs projecting from said outer side surface portion in twodiametrically opposed directions and two web sections each extendingabove the whole length of the two lugs of one of said pairs and rigidlyconnecting these two lugs to one another, each of said web sectionshaving an upper surface portion forming part of said polished upperouter conical surface portion.

11. A watch case as defined in claim 8, wherein said housing member hasat least one outer cylindrical bearing surface and a shoulder adjacentto said bearing surface and extending perpendicular thereto; whereinsaid metal carbide covering has at least one inner cylindrical bearingsurface and a shoulder adjacent and perpendicular thereto correspondingto said bearing surface and said shoulder of said housing member, andwherein said covering is rigidly fixed to said housing member by meansof glue interposed between said cylindrical bearing surfaces and saidshoulders.

12. A watch case as defined in claim 8, wherein said housing member isstainless steel .and includes a flat upper surface, two pairs ofoutwardly projecting wrist-band attaching lugs, each lug having a firstflat upper surface extending in the same plane as the firstmentioned'upper surface, and a second fiat upper surface inclineddownward with respect to the first mentioned fiat upper surface, thesecond surface of the two lugs of each of said pairs being located inthe same plane and wherein said metal carbide covering comprises a firstthin plate made of metal carbide harder than topaz and including anannular portion and two diametrically opposed ears, said first thinplate being rigidly fixed onto housing member with said annular portionand said ears of said first thin plate thereby exactly covering thefirst mentioned fiat upper surface, and said first fiat upper surface ofeach of said lugs, and two plates made of a metal carbide harder 7 8than topaz, each having the same thickness as said first 2,875,5743/1959 Dinstman 58-90 plate and being rigidly fixed to said second uppersnrfaces 3,097,897 7/1963 Taylor 29182.8 X of the two lugs of one ofsaid palrs, each of said two FO E N S plates thereby being in contactWith one of said ears.

5 447,373 3/1948 Canada.

References Cited by the Examiner 265,253 2/ 1950 Switzerland. UNITEDSTATES PATENTS 282,143 7/1952 Switzerland.

1,541,217 6/1925 Herbermann 5891 LEO SMILOW, Primary Examiner 2,120,5626/1938 Laise 75 -221 X 2,147,329 2/1939 Willey 75 221 X 10 JOSEPHI-STRIZAK,Exammer- 2,462,839 3/ 1949 Brown 5890 X GERALD F. BAKER,Assistant Examiner.

1. A WATCH CASE HAVING AN EXPOSED OUTER AREA CONTAINING A METAL CARBIDEAND BEING HARDER THAN TOPAZ.